1. Field of the Invention
The present invention generally relates to a fabrication method of nanoparticles. More particularly, the present invention relates to a fabrication method of nanorings.
2. Description of Related Art
As the advancements toward high precision and minuteness become the main trend in various types of industries, the tiny nanoparticles are nowadays considered as materials of tremendous potentials. Following the developments of the nanoparticle related technologies, the possible applicable ranges or uses of the nanoparticles have been rapidly extended in different industries. Sorting by the material of the nanoparticle, the nanoparticles may be made of metal or a dielectric material. The metal nanoparticles, possessing the capability of inducing localized surface plasmon resonance (LSPR), draw great attentions to their promising applications in biomedical fields.
In general, the metal nanoparticles include nanospheres, nanorods, nanorings, nanoshells and nanocages. Due to their unique geometries, the nanorings have the LSPR at longer wavelengths and the nanorings may have more extensive biomedical applications. Especially, the gold nanorings can have the LSPR wavelengths up to 1300 nanometers, at which light can achieve the deepest penetration into biological tissues, and hence have wide biomedical applications.
Conventionally, metal nanorings can be fabricated with the technique of plastic nanosphere lithography. However, it is nearly impossible to precisely control the size of each plastic nanosphere with the existing technology. Under the circumstances that the size of the available plastic nanosphere is not uniform, the size of the consequently formed metal nanoring is not uniform, that further has an impact on the LSPR wavelength ranges of the nanorings (for example, the wavelength distribution ranges of their LSPR are too large and their LSPR strengths are too weak).